rx and tx jumper on gps shield.

hye everyone! 

i'm using gps shield itead studio v1.1 in project. tomorrow turn present project panels. i'm still wondering, why have disconnect jumper on tx , rx pin on gps shield before uploading gps sketch fetch data? since sketch can not uploaded jumpers on shield. i'm preparing answers before being asked panels tomorrow. please me 

>>this coding i'm using>>>

code: [select]

#include <tinygps.h>

tinygps gps;

static void gpsdump(tinygps &gps);
static bool feedgps();
static void print_float(float val, float invalid, int len, int prec);
static void print_int(unsigned long val, unsigned long invalid, int len);
static void print_date(tinygps &gps);
static void print_str(const char *str, int len);

void setup()
{
  serial.begin(9600);
 
  serial.print("testing tinygps library v. "); serial.println(tinygps::library_version());
  serial.println("by mikal hart");
  serial.println();
  serial.print("sizeof(gpsobject) = "); serial.println(sizeof(tinygps));
  serial.println();
  serial.println("sats hdop latitude longitude fix  date       time       date alt     course speed card  distance course card  chars sentences checksum");
  serial.println("          (deg)    (deg)     age                        age  (m)     --- gps ----  ---- london  ----  rx    rx        fail");
  serial.println("--------------------------------------------------------------------------------------------------------------------------------------");
}

void loop()
{
  bool newdata = false;
  unsigned long start = millis();
 
  // every second print update
  while (millis() - start < 1000)
  {
    if (feedgps())
      newdata = true;
  }
 
  gpsdump(gps);
}

static void gpsdump(tinygps &gps)
{
  float flat, flon;
  unsigned long age, date, time, chars = 0;
  unsigned short sentences = 0, failed = 0;
  static const float london_lat = 51.508131, london_lon = -0.128002;
 
  print_int(gps.satellites(), tinygps::gps_invalid_satellites, 5);
  print_int(gps.hdop(), tinygps::gps_invalid_hdop, 5);
  gps.f_get_position(&flat, &flon, &age);
  print_float(flat, tinygps::gps_invalid_f_angle, 9, 5);
  print_float(flon, tinygps::gps_invalid_f_angle, 10, 5);
  print_int(age, tinygps::gps_invalid_age, 5);

  print_date(gps);

  print_float(gps.f_altitude(), tinygps::gps_invalid_f_altitude, 8, 2);
  print_float(gps.f_course(), tinygps::gps_invalid_f_angle, 7, 2);
  print_float(gps.f_speed_kmph(), tinygps::gps_invalid_f_speed, 6, 2);
  print_str(gps.f_course() == tinygps::gps_invalid_f_angle ? "*** " : tinygps::cardinal(gps.f_course()), 6);
  print_int(flat == tinygps::gps_invalid_f_angle ? 0ul : (unsigned long)tinygps::distance_between(flat, flon, london_lat, london_lon) / 1000, 0xffffffff, 9);
  print_float(flat == tinygps::gps_invalid_f_angle ? 0.0 : tinygps::course_to(flat, flon, 51.508131, -0.128002), tinygps::gps_invalid_f_angle, 7, 2);
  print_str(flat == tinygps::gps_invalid_f_angle ? "*** " : tinygps::cardinal(tinygps::course_to(flat, flon, london_lat, london_lon)), 6);

  gps.stats(&chars, &sentences, &failed);
  print_int(chars, 0xffffffff, 6);
  print_int(sentences, 0xffffffff, 10);
  print_int(failed, 0xffffffff, 9);
  serial.println();
}

static void print_int(unsigned long val, unsigned long invalid, int len)
{
  char sz[32];
  if (val == invalid)
    strcpy(sz, "*******");
  else
    sprintf(sz, "%ld", val);
  sz[len] = 0;
  (int i=strlen(sz); i<len; ++i)
    sz[i] = ' ';
  if (len > 0)
    sz[len-1] = ' ';
  serial.print(sz);
  feedgps();
}

static void print_float(float val, float invalid, int len, int prec)
{
  char sz[32];
  if (val == invalid)
  {
    strcpy(sz, "*******");
    sz[len] = 0;
        if (len > 0)
          sz[len-1] = ' ';
    (int i=7; i<len; ++i)
        sz[i] = ' ';
    serial.print(sz);
  }
  else
  {
    serial.print(val, prec);
    int vi = abs((int)val);
    int flen = prec + (val < 0.0 ? 2 : 1);
    flen += vi >= 1000 ? 4 : vi >= 100 ? 3 : vi >= 10 ? 2 : 1;
    (int i=flen; i<len; ++i)
      serial.print(" ");
  }
  feedgps();
}

static void print_date(tinygps &gps)
{
  int year;
  byte month, day, hour, minute, second, hundredths;
  unsigned long age;
  gps.crack_datetime(&year, &month, &day, &hour, &minute, &second, &hundredths, &age);
  if (age == tinygps::gps_invalid_age)
    serial.print("*******    *******    ");
  else
  {
    char sz[32];
    sprintf(sz, "%02d/%02d/%02d %02d:%02d:%02d   ",
        month, day, year, hour, minute, second);
    serial.print(sz);
  }
  print_int(age, tinygps::gps_invalid_age, 5);
  feedgps();
}

static void print_str(const char *str, int len)
{
  int slen = strlen(str);
  (int i=0; i<len; ++i)
    serial.print(i<slen ? str[i] : ' ');
  feedgps();
}

static bool feedgps()
{
  while (serial.available())
  {
    if (gps.encode(serial.read()))
      return true;
  }
  return false;
}

the bootloader , gps both use hardware serial port.  if gps sending messages serial port bootloader can't.

Arduino Forum > Using Arduino > Installation & Troubleshooting > rx and tx jumper on gps shield.

arduino